You have three sets of memories, and you can keep track of all three of them without skipping a beat.
You observe the birthdays and anniversaries of your alters by going out to eat and buying stuff for them.
You decipher cryptic messages that you wrote.
You hear the Christmas carol "Un Flambeau, Jeannette, Isabelle," and you say to yourself, "They're playing my song."
You're in a chat room with one of your alters, and she gets mad at you for bringing up her mom's car. How was I supposed to know I wasn't supposed to mention her mom's Mercedes Benz? Jeanette never said a word prior to then.
Your alter is talking with her cousin's friend in an open forum, but then that friend decides to move the conversation to private messaging.
Your alter does not like the high school graduation gift you gave her though you spent $250 on it.
Your alter is upset with a cartoonist because of something he did in his comic strip. You have no idea why she's upset, but you support her anyhow.
You're not French, but your alter is, and she defends French pride during the bashing of the French.
Your alter asks for mustard, but you don't like mustard.
One of your most cherished possessions does not exist in the physical world.
In the physical world, you buy a model of a white Mercury Colony Park because you once had that car in your interworld, though not in the physical world.

When a form asks for your birthday, you, several times, almost wrote down your alter's birthday.
You're shopping for a graduation card, but you leave the store before you can finish because you are so overwhelmed with emotion. After all, your alter, who once was a little girl, is now grown up.
All of a sudden, though you haven't colored in a coloring book since your body was a child, you buy crayons, coloring books and spend hours on end on the floor coloring in those coloring books.
Every couple has a song that is "their song." You often listen to your alter's parents' "song." In this particular case, it's "Faithfully" by Journey.
https://youtu.be/OMD8hBsA-RIYour body is in the early thirties, and you're listening to the Backstreet Boys. After all, your alter is a teenage girl.
You have dreams from your alternate personality's point of view.